Nasal mask with integral mouldable straps

ABSTRACT

A mask ( 10 ) for supplying gas under pressure to the nasal airway of a human includes a series of flexible stretchable straps ( 12, 14, 16 ) formed from an clastomeric material for locating the mask ( 10 ) against the human face. The straps ( 12, 14, 16 ) are integrally formed or joined to define a perimeter ( 18 ) enclosing an aperture ( 20 ) adapted to fit around the nasal area of a human. The straps ( 12, 14, 16 ) are configured to approximate to the three dimensional shape of the region around the nasal area of the human face as they arm strethed, to form a tight fitting seal. The mask may be used with or without a manifold.

FIELD OF THE INVENTION

[0001] This invention relates to a mask for supplying gases, typicallyfresh air or oxygen to the airways of humans.

BACKGROUND OF THE INVENTION

[0002] Various different types of masks are used to provide fresh air oroxygen to the airways of humans. A specialised category of masks is usedto provide positive pressure to the human airway. Positive pressureapplied in this manner has two different goals.

[0003] In a first category, positive pressure is applied to the lungsfor the purpose of stabilising the lungs, and in particular formaintaining a minimum inflation level of the small air spaces in whichgas transfer occurs (the alveoli). This therapy is very useful inpatients with a variety of lung diseases, where the disease process tendto lead to collapse (closure of the airway containing regions of thelung).

[0004] In a second category, the positive pressure is applied to thenasal airway with the intention of maintaining the pressure in, and thepatency of, the upper airway. This form of positive airway pressure isknown as nasal continuous positive airway pressure (nasal CPAP). This isnow the “gold standard” treatment for the condition known as obstructivesleep apnea (OSA), and also for snoring. Obstructive sleep apnea is acondition in which the upper airway closes in sleep, and does sorepeatedly. Nasal CPAP, when applied for the duration of sleep,stabilises the upper airway and allows for normal sleep and normalbreathing.

[0005] Masks for applying nasal CPAP, or nasal pressure supportventilation have a requirement to be able to deliver pressure and flowand maintain pressures within the mask without permitting leaks. Leaksare undesirable as they can allow the pressure in the mask to drop belowa therapeutic level. Leaks may also be an irritation particularly, ifthe leak causes jets of air/oxygen to be directed into the patient'seye. Leaks interrupt a patient's sleep which is undesirable asinterrupted sleep is known to be of much less value than uninterruptedsleep. Further, as the masks are for use during natural sleep, a highlevel of comfort in the fit of the mask is necessary.

[0006] One very common mask design includes three separate components asfollows:

[0007]1. A soft mouldable rubberised interface which comes in directcontact with the patient's facial skin.

[0008]2. A rigid manifold to which the soft interface is connected, andwhich covers the patient's nose. The manifold includes:

[0009] a) connector lugs to which straps from a harness are connected;

[0010] b) connections to an air delivery pipe; and

[0011] c) a number of relatively small holes or equivalent feature toprovide a controlled leak of air to the atmosphere.

[0012]3. A harness which goes around the head from which three or morestraps extend to connect to the lugs on the rigid manifold.

[0013] A seal is achieved by the mask being pulled onto the face by thestraps attached to the rigid manifold. The seal is achieved by the rimof the mask coming into contact with the skin. In this way, direct forceis applied via the straps (harnessed place around the head), andtransmitted through the rigid manifold. There are a number ofdisadvantages with this mask which are discussed in more detail belowfollowing a description of other, known mask types.

[0014] More recently, in order to achieve a good seal “bubble” type gasdelivery masks have been developed. One such mask is described inAustralian Patent No. 643994, dated May 16, 1991. The mask describedtherein has a face contacting portion which is formed from anelastomeric material and is shaped to define a large bubble or domeshaped chamber. When gas is delivered through the chamber, the chambertends to balloon outwardly and, when fitted to a patient, the facecontacting portion is caused to overly a region of the patient's faceand seal three dimensionally with the contours of the overlaid facialregion. For practical reasons the mask is integrated with a rigidshell-like moulding which does not contact the patient's face. The shellis provided to enable a gas supply line to be connected to the mask, tofacilitate fastening of the mask to a patient's face and to minimise therisk that movement of the gas supply line will disrupt the seal betweenthe mask and the patient's face.

[0015] Other earlier masks comprise a shell custom moulded to fit aroundthe individual nose for each patient, and either use a glue, oralternatively a soft inner part against which a tight fit is achieved.Once again, this type of mask may be held in place by straps and a headharness attached to the hard shell.

[0016] The main problems when designing a mask is that the mask must beable to achieve an air tight seal with the subject's face and at thesame time be sufficiently comfortable to be able to be worn for hourswithout causing discomfort to the subject and in particular to allow thesubject to sleep.

[0017] Movement of the head, and subsequent dislodgment of the mask, andbreakage of the seal are major problems with prior art masks. This is aparticular problem when a patient lies on their side, with the side oftheir head on the pillow as the rigid manifold tends to contact thepillow The contact moves the manifold relative to the patient's face, istransmitted to, and affects the integrity of the seal and also themanifold can be pushed onto the patient's nose causing discomfort to thepatient.

[0018] Using the first type of mask as described above, which includesthe three separate components, seal breakage is addressed by pulling thestraps firm. This however, can lead to discomfort for the patient.

[0019] In the second mask type described above (the “bubble type mask”),the bubble provides a continuous rolling seal, so that minor head andother movements are accommodated within the excess thin membraneHowever, large head movements may not be accommodated by the rollingseal.

[0020] A major problem for all masks is that an air delivery pipe mustbe attached to the mask at some point. Movement of the head and the pipeleads to torsion which is transmitted through the hard shell of themanifold and can cause the sealing margins of the mask to rise up andallow a leak. The above-referenced “bubble mask” patent, (Australianpatent No 634994), tries to address this by having a “universal joint”between the air delivery pipe and the rigid manifold. Australian PatentNo 684412, by the same inventor as the earlier Australian patent No634994, addresses this problem by making a portion of the wallcontaining the gas supply port exhibit a degree of flexibility that isgreater than that of adjacent regions of the mask so that movement bythe connecting gas supply line will be accommodated at least in part byflexing of the wall portion. Whilst both masks produce relativelysatisfactory seals they are quite bulky, relatively heavy and ungainly.

[0021] In existing masks, because the straps must anchor onto a rigidpoint, they are attached to the rigid manifold; the result is thattypically the strap leaves the side of the face near the cheeks, andpasses through air until it reaches the lug on the manifold. This“floating” part of the strap, provides a significant weakness andadversely affects the integrity of the seal when the patient's headmoves When the subject rolls onto their side, this floating part of thestrap is easily distorted, and pulls on the mask and leads to a leak.

[0022] In one aspect, the present invention seeks to provide an improvedmask which reduces the relative size, weight and bulk of the existingmasks and yet provides a satisfactory seal.

[0023] A variant of the mask may be used to supply treated air, oxygenor an air/oxygen blend or the like to patients. In a known techniquesuch treated air is supplied from a pipe located near a patient's nasalairway and the flow of air is directed past the patient's nares. Thus,in a related aspect the present invention seeks also to provide harnessfor supporting a pipe for supplying a flow of gas to a patients nasalairway.

SUMMARY OF THE INVENTION

[0024] Thus in a first broad aspect of the present invention, there isprovided a mask for supplying gas under pressure to the nasal airway ofa human, including:

[0025] a series of flexible stretchable straps formed from anelastomeric material for locating the mask against the human face, thestraps being integrally formed or joined to define a perimeter enclosingan aperture adapted to fit around the nasal area of a human, the strapsbeing shaped and configured to approximate to the three dimensionalshape of the region around the nasal area of the human face; and

[0026] a manifold disposed on the non-face contacting side of the facecontacting portion, the manifold including means for connection to a gassupply means;

[0027] the arrangement being such that stretching of the straps aroundthe nasal area of the human causes the straps to mould to the contoursof the nasal area of the face so that the straps form a seal around thenasal area which is a relatively tight fitting seal.

[0028] In the present invention instead of providing a separate sealingmembrane and support shell, the straps themselves provide the seal. Thisgreatly reduces the size and weight of the mask. The patient's noseextends into the manifold. The straps closely fit to the patient's faceand the problems of flexing due to the connection with the air deliverypipe are reduced.

[0029] Straps for attachment to a head harness are used to define,locate and provide a seal around the perimeter of a patient's nose.Because the straps are sufficiently flexible they can mould around theperimeter, and in doing so, as the mask stretches around the margins atight fitting comfortable seal is achieved,

[0030] The mask of the present invention, allows the straps to pass overthe patient's cheeks, rather than “extending” through air down the sideof their heads. This provides a more secure fit of the mask and makesthe mask less likely to move.

[0031] The aperture may be generally triangular.

[0032] The mask may further include a flexible sealing element extendingalong one inwardly facing side of each strap. The sealing element may begenerally convex.

[0033] In one embodiment, a channel extends around the perimeter inwhich an adhesive means (such as “DuoDerm” or Elastogel”) for sealablyadhering the perimeter to the human facial area and minimising leakage,is provided

[0034] It is a significant advantage of the present invention that themask can be made in fewer parts than the mask of AU 684412, typicallyonly two, with the straps and sealing element moulded in one part andthe manifold in second part, which can make manufacture of the masksimpler and cheaper.

[0035] Typically, three flexible arms extends away from the straps forsecuring the face-contacting portion to a patient's head or face.

[0036] It is preferred that a pad is defined at the end of each flexiblearm distal from the plate. The pad may define slots so as to beconnectable to harness straps attached to a cap. These harness strapscould be connected to the pads by fastening materials such as velcro orthe like

[0037] In a particularly preferred embodiment, the pads, straps andsealing element are all integrally moulded from an elastomeric material,typically a high tear resistant silicone elastomer such as Silastic(Registered Trade mark of the Dow Corning Corporation) or Santoprene(Registered Trade Mark of Monsanto Co). The thickness of the straps istypically between 2 to 4 mm.

[0038] Typically, a number of small holes will be defined on themanifold to provide a constant leak to atmosphere and thus a way out forexpired air. The number and size of the holes are determined by thepressure of air supplied to the mask and flow delivery system and arechosen to enable the desired pressure and air flow through the mask.

[0039] In a particularly preferred embodiment, part of the manifoldextends along one of the arms of the mask, typically the arm whichextends from the top of the mask where an air port or hole for receivinga gas delivery pipe is provided.

[0040] The provision of the air port at the end of one of the arms ofthe mask greatly reduces the torsion effects on the mask due to the airdelivery pipe.

[0041] The manifold is typically made of the same thin flexibleelastomeric material that is used for the straps. Typically, thematerial forming the manifold is about 1 mm thick.

[0042] The manifold should ideally be somewhat larger than a typicalhuman nose. In this manner when a person lies on their side with theside of their head on a pillow, movement of the head can be accommodatedby flexing and compression of the manifold. Because the manifold is softand flexible, this movement is not transmitted to the seal but islargely absorbed by flexing of the manifold. Also because the manifoldis flexible, any contact of the manifold with a patient's nose shouldnot cause discomfort to the patient.

[0043] In one particularly preferred embodiment, the mask includes aharness and an air pipe extending to a junction port attachable to thetop of a patient's head and an air delivery pipe is rotatably mounted tothat junction port, thus allowing a patient's head to turn withoutmoving the air delivery pipe.

[0044] The present invention also encompasses a method of supplying gasto the airway of a human using any of the aspects or embodiments of theinvention described above.

[0045] Typically the method will be used to supply oxygen or air to theairway for nasal CPAP, or nasal ventilation or nasal pressure support.

[0046] However, in a related aspect a variant of the mask may be used tosupply treated air, oxygen or an air/oxygen blend or the like topatients wherein the mask is open or merely acts as a harness or anchorfor air pipes for directing a flow of air past the patients nares andfor creating a zone of clean air around a patient's nares.

[0047] Thus in a second aspect of the present invention there isprovided a harness for supplying gas under pressure to the nasal airwayof a human, including:

[0048] a series of flexible stretchable straps formed from anelastomeric material for locating the harness against the human face,the straps being integrally formed or joined to define a perimeterenclosing an aperture adapted to fit around the nasal area of a human,the straps being shaped and configured to approximate to the throedimensional shape of the region around the nasal area of the human face;and

[0049] a means for supplying a flow of gas directed generally towardsthe perimeter of the harness including means for connection to a gassupply means;

[0050] the arrangement being such that stretching of the straps aroundthe nasal area of the human causes the straps to mould to the contoursof the nasal area of the face so that the straps anchor the harness tothe human face relatively tightly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The invention will now be described by way of example only andwith reference to the accompanying drawings in which:-;

[0052]FIG. 1 is an isometric view of a mask embodying the presentinvention, but without a manifold;

[0053]FIG. 2 is a side view of the mask shown in FIG. 1;

[0054]FIG. 3 is a bottom plan view of the mask shown in FIG. 1; and

[0055]FIG. 4 is an isometric view of a manifold for the mask shown inFIGS. 1 to 3;

[0056]FIG. 5 is a side view of the manifold shown in FIG. 4;

[0057]FIG. 6 is an isometric view of a complete mask combining the maskof FIGS. 1 to 3 and the manifold of FIGS. 4 and 5;

[0058]FIG. 7 is a section through the mask of FIG. 6;

[0059]FIG. 8 is a schematic drawing illustrating a head mounted junctionport for receiving an air delivery pipe;

[0060]FIG. 9 shows a variant of the mask of FIG. 6;

[0061]FIG. 10 shows an isometric view of a variant of the mask of FIG.1; and

[0062]FIG. 11 shows an underneath plan view of the variant of FIG. 10.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0063] Referring to the drawings, FIG. 1 shows a part 10 of a mask. Themask includes three straps, 12, 14, 16 which are integrally moulded witha generally triangular face engaging portion or perimeter 18 enclosing agenerally triangular aperture 20. The straps can be considered to be anextension of members defining the perimeter as the straps 12, 14, 16 areintegrally formed and connected via the perimeter. Thus straps 12 and 14are connected via perimeter member 22, and pulling on the ends of straps12 and 14 also stretches perimeter member 22. Likewise, straps 12 and 16are integrally formed and connected by perimeter member 24, and straps16 and 14 by perimeter member 26. The perimeter 18 is integrally formedwith the straps from a flexible stretchable elastomeric material (suchas Silastic or Santoprene) and when the straps are stretched in adirection as shown by the arrows A, B and C, then the face engagingportion perimeter stretches also and the aperture 20 enlarges slightly.

[0064] As can be seen in FIGS. 2 and 3, the face engaging portion 18 ofthe mask and the straps themselves, particularly the top strap 16, aremoulded so that they tend to approximate to the contours of a humanface. Thus the upper part of the face engaging portion includes agenerally concave portion 30 which fits tightly over the bridge of apatient's nose.

[0065] The ends of the straps define pads 32 which include slots 34 forattachment to a harness (not shown) which fits around the back of aperson's head for stretching the mask over a person's nose. The strapsand perimeter may be between 2 mm to 4 mm thick.

[0066]FIGS. 4 and 5 illustrate a manifold 40 which defines an open face42 which defines an open face 42 which sealingly mates with the non-faceengaging side 10A of the mask 10 and the two components 10 and 40 may beglued or otherwise fixed together to form a complete mask 50 as shown inFIGS. 6 and 7. The manifold is flexible and compressible in contrastwith the prior art, allowing movement of a patient's head lying side-onon a pillow, to be accommodated by compression or deformation of themanifold. As is best seen in FIG. 7, an air port 52 for connection to anair delivery pipe is located at a distal end of the strap 16 remote fromthe aperture 10.

[0067] Around the inside of the perimeter 18, there is an additionalthinner, more flexible sealing element 54 best seen in FIG. 7. Thismembrane may be 1 mm thick or less.

[0068] The principal of operation of the mask. is similar to that ofpulling on a tight fitting garment. The nose and its surrounds could beconsidered to be a cone and the perimeter 18 is an elastic funnel shapedto approximate to the cone yet with slightly smaller margins and an opencentral region. As it is pulled over the cone, as the straps 12, 14, 16are tightened, the inner margins of the funnel contact the surface ofthe cone and then stretch around it causing a closed seal. The marginsof the mask are the perimeter members. As these members stretch, theypull inwards to the skin on the face and are at all times in directcontact with the skin. This is in direct contrast to the operation ofthe straps in the conventional masks and the bubble type masks where themasks are attached to a lug on a rigid manifold and extend for asubstantial distance in mid air, not in contact with a person's face,before they contact a person's face usually on the back of their cheekclose to their ears.

[0069] Since, in the present invention, the straps are always in contactwith the skin, this provides a much greater stability of the mask on theface. The straps also provide a seal having a large sealing or contactarea. The additional thinner flexible sealing element 54 improves theseal provided by the stretching of the face engaging portion. However,it is not critical to the performance of the mask and could be omitted.

[0070]FIG. 8 illustrates a variant of the invention where a short pipe60, which may be an extension of the manifold and strap 16 extends to anair port junction 62 fixed to the top of a patient's head. An elbow pipe64 is rotatably mounted in the air port junction 62 rotating about axisZ perpendicular to the top of the patient's head. The elbow 64 isconnected to an air delivery pipe 66. With this arrangement, thepatient's head can turn without being affected or affecting deliverypipe 66.

[0071] In a yet further variant, additional slots 34 are provided in thepads 32 of the arms 12 and 14 to receive the ends of a chin strap.

[0072]FIG. 9 illustrates a variant 100 of the mask of FIG. 6. The maskof FIG. 9 is used for supplying clean filtered air, treated air, or anair/oxygen blend to a patient where it is not necessary or desirable forthe patient to wear a closed mask enclosing the patient's nose. Closedmasks tend to uncomfortable when worn for long periods of time. Furtherif humid air is supplied by a closed mask to an asthma sufferer forexample, water will tend to condense inside the closed mask which isundesirable. In this embodiment the manifold is replaced by a canopy orhood 102 which directs air under pressure 104 down the canopy towardsthe patient's nares. The base 106 of the canopy is open, being eithertotally open, or as illustrated in FIG. 9 defining a large number ofrelatively large diameter holes 108 typically having a diameter of about5 mm to 10 mm or more. In use when the harness is worn the patient'snose is located under the canopy 102 and the patient's nares areadjacent the base 106 of the canopy, The straps which are always incontact with the skin this provide a very stable anchoring of the maskon the face. However in contrast with the mask of FIGS. 1 to 8, no sealis required. This arrangement allows a relatively high volume fast flowF of low pressure air past a patient's nares and creates an atmospherearound the nares which is dominated by the low pressure air orair/oxygen mix. The canopy is preferably transparent as shown in FIG. 9.The same effect may be created by simply forming a large number ofrelatively large diameter holes, say 5 to 10 mm or more in the base ofmanifold of the mask of FIG. 6.

[0073] In the embodiment of the mask/harness 150 shown in FIGS. 10 and11, pipes 152, 154 extend along each of the straps 12, 14 respectivelyand terminate in open ends 156, 158 adjacent the perimeter 18 of themask/harness. In use when the harness is worn the patient's nose extendsthrough the perimeter 18. The straps which are always in contact withthe skin provide a very stable anchoring of the mask on the face. Againin contrast with the mask of FIGS. 1 to 8, no seal is required. A flowof pressurised filtered clean air passes along the pipes 12 14 as shownby the arrows F. This flow creates a ‘virtual space’ or zone of cleanfiltered air around the patient's nose N and nares NS shown in dashedoutline in FIG. 10.

[0074] It will be appreciated by persons skilled in the art thatnumerous variations and/or modifications may be made to the invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects as illustrative and notrestrictive.

1. A mask for supplying gas under pressure to the nasal airway of ahuman, including: a series of flexible stretchable straps formed from anelastomeric material for locating the mask against the human face, thestraps being integrally formed or joined to define a perimeter enclosingan aperture adapted to fit around the nasal area of a human, the strapsbeing shaped and configured to approximate to the three dimensionalshape of the region around the nasal area of the human face; and amanifold disposed on the non-face contacting side of the face contactingportion, the manifold including means for connection to a gas supplymeans; the arrangement being such that stretching of the straps aroundthe nasal area of the human causes the straps to mould to the contoursof the nasal area of the face so that the straps form a seal around thenasal area which is a relatively tight fitting seal.
 2. A mask asclaimed in claim 1 wherein the aperture is generally triangular.
 3. Amask as claimed in any preceding claim further including a flexiblesealing element extending along one inwardly facing side of each strap.4. A mask as claimed in claim 3 wherein the sealing element is generallyconvex in cross-section.
 5. A mask as claimed in any preceding claimwherein a channel extends around the perimeter in which an adhesivemeans for sealably adhering the perimeter to the human facial area andminimising leakage, is provided
 6. A mask as claimed in any precedingclaim wherein three flexible arms extend away from the perimeter forsecuring the face-contacting portion to a patient's head or face.
 7. Amask as claimed in claim 6 wherein a pad is defined at the end of eachflexible arm distal from the perimeter.
 8. A mask as claimed in claim 7wherein each pad defines slots so as to be connectable to harness strapsattached to a cap.
 9. A mask as claimed in any preceding claim whereinthe straps and sealing element are integrally moulded from anelastomeric material.
 10. A mask as claimed in any preceding claimwherein the thickness of the straps is from 2 to 4 mm.
 11. A mask asclaimed in any preceding claim wherein a plurality of small holes havinga diameter of up to 5 mm are defined on the manifold to provide aconstant leak to atmosphere.
 12. A mask as claimed in any one of claims6 to 11 wherein the manifold extends along one of the arms of the mask,most preferably the arm which extends from the top of the mask where anair port or hole for receiving a gas delivery pipe is provided.
 13. Amask as claimed in any preceding claim wherein the manifold is made ofthe same thin flexible elastomeric material that is used for the strapsand wherein the material forming the manifold is 0.75 to 1.5 mm thick,preferably about 1 mm thick.
 13. A mask as claimed in any precedingclaim wherein the manifold includes a plurality of large diameter holes.14. A harness for supplying gas under pressure to the nasal airway of ahuman, including: a series of flexible stretchable straps formed from anelastomeric material for locating the harness against the human face,the straps being integrally formed or joined to define a perimeterenclosing an aperture adapted to fit around the nasal area of a human,the straps being shaped and configured to approximate to the threedimensional shape of the region around the nasal area of the human face;and a means for supplying a flow of gas directed generally towards theperimeter of the harness including means for connection to a gas supplymeans; the arrangement being such that stretching of the straps aroundthe nasal area of the human causes the straps to mould to the contoursof the nasal area of the face so that the straps anchor the harness tothe human face relatively tightly.
 15. A harness as claimed in claim 14wherein the aperture is generally triangular.
 16. A harness as claimedin any one of claims 14 to 15 wherein three flexible arms extend awayfrom the perimeter for securing the face-contacting portion to apatient's head or face.
 17. A harness as claimed in claim 16 wherein apad is defined at the end of each flexible arm distal from theperimeter.
 18. A harness as claimed in claim 17 wherein each pad definesslots so as to be connectable to harness straps attached to a cap.
 19. Aharness as claimed in any one of claims 14 to 18 wherein the straps andsealing element are integrally moulded from an elastomeric material. 20.A harness as claimed in any one of claims 14 to 19 wherein the thicknessof the straps is between 2 to 4 mm.
 21. A harness as claimed in any oneof claims 16 to 20 wherein a pipe extends along at least one, andpreferably two of the arms, the pipe or pipes terminating in an open endadjacent the perimeter.
 22. A method of supplying a gas to the airway ofa human using a mask or harness as claimed in any preceding claim.